Ultrasound is used to check for cracks inside metal parts.
A probe is placed on the top surface of a steel block. The block is 0.24 m thick. The probe sends a pulse of ultrasound down into the block and detects the echoes.
The speed of ultrasound in steel is 6000 m/s.
The Table shows the times at which two echoes are detected.
Table
| Echo | Time after pulse is sent in μs\mu\text{s}μs |
|---|---|
| echo 1 | 30 |
| echo 2 | 80 |
Show that echo 2 is from the bottom surface of the block.
Echo 1 is from a crack inside the block.
Calculate the depth of the crack below the top surface of the block.
A second steel block, with the same thickness, has no crack.
Describe how the echoes detected from this block would be different.
The ultrasound has a frequency of 5.0 MHz.
Calculate the wavelength of the ultrasound in steel.
112 exam-style questions on Edexcel GCSE Physics 4.3 Sound, ultrasound and infrasound, covering 4.3.1 Sound waves, vibrations and the human ear, 4.3.2 Ultrasound and infrasound, 4.3.3 Uses of ultrasound and infrasound, and 4.3.4 Sound waves passing between media. Each one has a worked solution and a mark scheme showing where the marks go.